Russian Journal of Physical Chemistry A最新文献

CuO–Mn₂CuO₄ composite materials for tailored hydrogen evolution were successfully synthesized using a simple method. The synthesis process used Cu(NO₃)₂⋅3H₂O and MnCO₃ as precursors. The resulting composites were comprehensively characterized using a suite of analytical techniques, including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X‑ray diffraction. The electrochemical performance of the CuO–Mn₂CuO₄ composites was systematically evaluated through cyclic voltammetry and linear sweep voltammetry, while electrochemical impedance spectroscopy was used to investigate the hydrogen evolution reaction at the electrode interface. The composite demonstrated a 0.31 V reduction in overpotential compared to the bare glassy carbon electrode, with a hydrogen evolution rate of approximately 0.76 mL min^–1 cm^–2, with a current density of 100 mA cm^–2, which was approximately three times that of the GCE.

In this research, the performance of polyethylene glycol (PEG) as a nanocarrier for the targeted drug delivery of cyclophosphamide (CLP) was investigated by density functional theory, infra-red, frontier molecular orbital and natural bonding orbital computations. The achieved results showed the interaction of CLP with PEG is experimentally feasible. The calculated thermodynamic parameters showed CLP adsorption process is spontaneous, exothermic and two sided. The impact of temperature and solvent on the interactions was also checked out and the results showed the presence of water as the solvent does not affect the interactions. Besides, by increasing of temperature CLP interactions with adsorbent become weaker indicating PEG can be employed as a temperature sensitive drug carrier. The increasing of dipole moment and also the decline of chemical hardness and bandgap showed when CLP adsorbs on the surface of PEG its chemical reactivity and bioavailibity improves substantially. The natural bonding orbital results demonstrated CLP interaction with PEG has a physisorption nature.

Abstract—In continuation of previous published works on the synthesis and crystallographic characterization of dioxouranium complexes with symmetrical NNOO tetradentate Schiff bases, we report herein deep investigations of the supramolecular features, and electrochemical properties of the studied crystal. This includes 3D molecular Hirshfeld surface analysis and visualization of the resulting three-dimensional supramolecular network. The analysis identifies H⋅⋅⋅C/C⋅⋅⋅H contacts as the main contributors to crystal packing, accounting for 34.7%. The 3D supramolecular network of LUO₂ is formed through the overlap of chains, resulting in a porous structure along the (Oa) direction. The pores are uniform, non-circular, and approximately 9 Å in size along the shorter diagonal. In addition, the electrochemical properties of the uranyl complex, studied via cyclic voltammetry, revealed a quasi-reversible U(VI)/U(V) redox process with a half-wave potential (E_1/2) of –1126 mV vs. SCE in DMF. Measurements using a glassy carbon electrode indicated diffusion-controlled redox behavior. Thermal studies indicate that the complex is non-volatile and a high thermal stability.

Mechanochemical synthesis of silicon oxycarbide composites based on mixtures of activated carbon and silica gel with different mass ratios has been performed. It was established that the obtained materials have a homogeneous amorphous structure and sufficiently developed porosity. The acid-base properties of the surface are determined by the phenol, carboxyl, and silanol groups of various configurations, with the greatest contribution from the groups with pK_a 8.5–12. An increase in the concentration of these groups with a simultaneous decrease in the concentration of groups with pK_a 0–5 results in an increase in the pH value at the zero charge point. Due to electrostatic interactions, the synthesized composites adsorb methyl orange more efficiently than they adsorb methylene blue. The highest adsorption capacity with respect to methyl orange (286.2 mg/g) was shown by the sample obtained from a mixture with a mass ratio of activated carbon to silica gel of 1 : 2.

The applicability of iron oxide powder, a waste product from the production of organic dyes, as a raw material for obtaining oxide catalysts has been studied. The physicochemical characteristics of the starting material and the samples after various types of treatment (mechanochemical activation (MA), ultrasonic treatment in an oxalic acid solution) were studied by X-ray diffraction analysis, Mössbauer spectroscopy, scanning electron microscopy, and low-temperature nitrogen adsorption. It was established that the optimum physicochemical characteristics are achieved with combined processing: ultrasonic dissolution in oxalic acid followed by calcination at 425°C. The use of mechanochemical activation and ultrasonic treatment allows us to regulate the composition and properties of the resulting oxides (substructural characteristics, particle size, specific surface area, and porous structure). The use of these processing methods allows us to control the formation of optimum properties required for the majority of the catalysts of conversion of carbon monoxide with water vapor and biomass pyrolysis.

The commercial samples of the second-generation rodenticidal substance bromadiolone (I) have been studied by UV and IR spectroscopy, RP HPLC, and X-ray diffraction (XRD). Conditions for identification of the isomeric composition by RP HPLC were preliminarily selected, which made it possible to divide the samples into groups differing in the isomeric (cis-/trans-) composition of I in the range from 82 : 18 to 72 : 28 (to 64 : 36 in the products). Some aspects of sample preparation and the results of the analysis of various formulations/products containing I are presented. Two different crystalline phases, Ia and Ib, were isolated from the amorphous commercial substances and characterized by a complex of physicochemical methods (IR, XRD, DTA, PPM), and comparative efficiency data were obtained. The crystal structure of Ib was determined by XRD analysis. An attempt to isolate I from various solvent systems based on dimethyl sulfoxide led to crystallization of phases that are the products of destruction and rearrangement. Under production conditions, heating in this particular solvent gives highly concentrated forms (premixes) of I, which are used to prepare poisoned rodenticidal baits. An analysis of the XRD data showed that in addition to the expected salicylic acid, the rearrangement products were cyclic derivatives: triacetone triperoxide and γ-butyrolactone II with bulky substituents in the third and fifth positions. Direct synthesis of II is difficult because of the presence of bulky substituents, but can be achieved via direct rearrangement of I, as found in the course of the present work. Apparently, homologs of γ-butyrolactone with other substituents can be obtained using substances related to bromadiolone.

The Fenton reaction is of considerable interest because it can be used in chemical, biochemical, and biomedical research. The Fenton reaction allows us to estimate the content of hydroperoxides in a sample. Such studies require knowledge of the characteristics of the reaction at different ratios between concentrations of hydroperoxides and divalent iron. The yield of the reaction is determined from its сhemiluminescence. The number of oxidation acts of N(Fe²⁺ → Fe³⁺) in the Fenton reaction is calculated for cases of [Fe²⁺] > [H₂O₂] and [Fe²⁺] < [H₂O₂] at concentrations of Fe²⁺ and H₂O₂ ranging from 10⁻³ to 10⁻⁷ mol/L. It is shown that the concentration of peroxide can be determined unambiguously only when [Fe²⁺] > [H₂O₂]. With [Fe²⁺] < [H₂O₂], it is not always possible to determine the complete yield of сhemiluminescence due to a strong drop in the rate of the reaction. The kinetics behind the formation of the luminous product in the Fenton reaction after introducing luminal to enhance the glow is calculated.

The complexation in the [ReOCl₅]^2––Ox/Red–HCl system (Ox is bis-N-ethylformamidine disulfide (H₂DEfds²⁺), and Red is N-ethylurea (Etu)) was studied by potentiometric titration in the temperature range of 273.1–338.1 K, and the (log {{K}_{i}}) values of the complexes were determined. The thermodynamic values of this process (ΔH⁰, ΔG⁰, and ΔS⁰) were calculated using the (log {{K}_{i}}) values. The process exothermicity was found to decrease with an increase in the number of coordinated ligand molecules. The most favorable condition for the formation of stable complexes is the concentration of 4 M HCl; i.e., when the concentration of hydrochloric acid decreases from 6 to 4 M HCl, the stability of the resulting complexes increases.

The use of IR spectrometry and X-ray diffractometry for evaluating the crystallinity of the active components of hydrogenation catalysts deposited on alumina in the α- and γ-Al₂O₃ modifications is considered. The possibility of using IR spectroscopy in a comprehensive approach to qualitative and quantitative evaluation of the crystallinity of CuO and NiO in the catalysts is substantiated. Copper and nickel catalysts supported on α- and γ-Al₂O₃ were synthesized and tested. The crystallinity was evaluated using the characteristic absorption bands in the IR spectra: 1480 and 450 cm^–1 bands for NiO and 1320 and 422 cm^–1 for CuO. The experimental data showed that the crystallinity of the active phase has a significant effect on the catalytic activity in the hydrogenation reaction. The structure of the substrate (α- or γ-Al₂O₃) affects the distribution and state of metal phases, which also affects the activity of the catalysts.

Composite sorbents based on chitosan and containing silica and topinambur, as well as carbon nanotubes, have been developed for extracting heavy metal ions from aqueous solutions. The equilibrium and kinetics of copper(II) ion extraction in the “aqueous solution of metal sulfate–sorbent” heterophase system were studied for the initial chitosan powder and for the modified sorbents obtained in the form of hydrogel granules. In a kinetic experiment, the time required to reach the sorption equilibrium was determined, and a kinetic model was established that describes the process most accurately. The experimental sorption isotherms indicate a significant increase in the sorption capacity of the chitosan-based composites compared to that of the original sample. As a result of processing the sorption isotherms of copper(II) ions according to the Langmuir model, the maximum sorption capacities of the sorbents (A_∞) were determined. It was established that A_∞ of the chitosan/silica/topinambur and chitosan/carbon nanotubes composite sorbents significantly exceed A_∞ for the original chitosan. The changes in the composition of the sorbents as a result of modification compared to the starting chitosan are confirmed by IR spectral data. The SEM studies showed the presence of a developed surface structure of the granules of chitosan-based composite sorbents.